Wait for incoming ethereum transactions and credit them after n confirmations

Question

I'm trying to create a website where users can deposit ethereum. For my server I'm using node.js and express.js. I looked into web3.js but the docs are unclear to me and I don't know which functions to use. I guess having a background loop running and checking for incoming transactions, then create another loop which waits for the nth confirmation is the way to go. But which package and functions should I use for achieving this? Can someone sort me out where to start?

Answer 1

I have an example with ethers.js:

const ethers = require("ethers");

// Change the provider if needed. Mine is my local Ganache
const provider = new ethers.providers.JsonRpcProvider("http://localhost:7545");

const signer = provider.getSigner();

async function sendTransactionAndWait5Confirmations() {
  const tx = await signer.sendTransaction({
    // Change the 'to' address to one available in your local network or your provider
    to: "0xd2826D22cfA01d6cA6730b60A895d8c231E6385b",
    // Sending 3 ethers
    value: ethers.utils.parseEther("3.0"),
  });

  // Waiting 5 confirmations. You can put any number of confirmations here
  const txReceipt = await tx.wait(5);

  console.log("txReceipt: ", txReceipt);
}

sendTransactionAndWait5Confirmations();

Create a directory, create an index.js file, run the command:

npm install ethers

Put the code in the index.js file.

My provider http://localhost:7545 is where my local Ganache is running. Run Ganache and check where it is running:

Change the to: "0xd2826D22cfA01d6cA6730b60A895d8c231E6385b" to any address of the ones shown in Ganache. Not the first one because that will be the sender by default.

Then run:

node index.js

This will stop on the line const txReceipt = await tx.wait(5); and wait for 5 confirmations, for 5 blocks, the one where the transaction is included + 4 more blocks.

Since this script is busy, we need to generate blocks somehow so we get the required 5 confirmations and finally see the txReceipt. For this, I simply connected Remix to my local Ganache and deployed a few contracts and at 5 confirmations the script continued and showed the txReceipt.